KDE 2/Qt Programming Bible phần 3 pdf

4682-1 ch06.f.qc 11/13/00 14:10 Page 127 Chapter ✦ Menus and Toolbars The method createStatusBar() on line 36 calls statusBar() to create and install a widget capable of displaying a single line of text Your program has access to the text of the status bar, so it can keep it constantly updated Unlike the toolbar and the menu bar, the status bar cannot be moved to another location The method createToolBar() on line 41 creates a toolbar by calling toolBar() on line 43 An ID number is required as an argument because your application can have as many toolbars as you would like You supply the ID number and, if there is no toolbar with that ID, one is created and returned Using the same ID number will always return the same toolbar For this example, a pixmap is used to create a single toolbar button The toolbar can be moved outside of its parent window Figure 6-3 shows the result of using the handle at the left end of the toolbar to “tear off” the menu from its parent window and establish it as its own stand-alone window Figure 6-3: Tear-off menus and toolbars The method named slotExit() on line 47 is called whenever the user selects Exit from the menu You may need to some kind of cleanup here and save currently unsaved data, but this example simply calls the exit() method in the application The global variable named kapp always contains a pointer to the KApplication object The slot method named queryClose() on line 51 is called when the figure X in the upper right corner of the application’s frame is selected If this slot returns TRUE, the application is immediately closed If it returns FALSE, no action will be taken (the signal from the X button will be ignored) This is the skeleton of an application Allowing KTMainWindow to most of the work, your top-level window can be very sophisticated with only a few lines of code The rest of this chapter describes the details of configuring the menu bar and toolbars, and displaying information via the status bar 127 4682-1 ch06.f.qc 128 11/13/00 14:10 Page 128 Part I ✦ Getting Started The Menu Bar Basically, a menu is a collection of buttons with a slot attached to each one The dynamics of a menu simplifies access to the buttons by making a specific subset of them available at any one time There are different ways of organizing and decorating the buttons The following example creates the window shown in Figure 6-4 This menu bar was contrived to demonstrate the different things you can use in the construction of a menu Figure 6-4: An application with a menu bar at the top The header file mostly contains declarations of slots that will be called whenever a menu button is selected, but there is also some private data that is needed to track the status of menu buttons that are toggled from one state to another The MenuMain class inherits from the KTMainWindow class, so it already has the capability to display and manage a menu MenuMain Header 10 11 12 13 14 15 16 17 18 19 20 21 22 23 /* menumain.h */ #ifndef MENUMAIN_H #define MENUMAIN_H #include #include #include #include class MenuMain: public KTMainWindow { Q_OBJECT public: MenuMain(); private: QPopupMenu *checkPopup; int enableColorsID; int enableGraphicsID; private slots: void slotExit(); bool queryClose(); void slotNew(); void slotSave(); 4682-1 ch06.f.qc 11/13/00 14:10 Page 129 Chapter ✦ Menus and Toolbars 24 void slotSaveAs(); 25 void slotClose(); 26 void slotLogo(); 27 void slotSub(); 28 void slotEnableColors(); 29 void slotEnableGraphics(); 30 private: 31 void createMainWidget(); 32 void createMenu(); 33 }; 34 35 #endif MenuMain 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 /* menumain.cpp */ #include #include #include #include #include #include “menumain.h” int main(int argc,char **argv) { KCmdLineArgs::init(argc,argv,”menumain”, “Menu Main”,”0.0”); KApplication app; MenuMain *menumain = new MenuMain(); menumain->show(); return(app.exec()); } MenuMain::MenuMain() : KTMainWindow() { createMainWidget(); createMenu(); } void MenuMain::createMainWidget() { QPushButton *button = new QPushButton(“Top Level\nWidget”,this); QWhatsThis::add(button, “Button\n\n” “This button is used as the top\n” “level widget for this example It\n” “is very safe to click the button\n” “because it doesn’t anything.\n”); setView(button); } void MenuMain::createMenu() { 129 4682-1 ch06.f.qc 130 11/13/00 14:10 Page 130 Part I ✦ Getting Started 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 QPopupMenu *popup; QPopupMenu *popup2; QPixmap pixmap; KMenuBar *menubar = menuBar(); popup = new QPopupMenu(); popup->insertItem(“&New”,this, SLOT(slotNew()),ALT+Key_N); popup->insertItem(“&Save”,this, SLOT(slotSave()),CTRL+Key_S); popup->insertItem(“Save As”,this, SLOT(slotSaveAs()),CTRL+SHIFT+Key_S); pixmap.load(“flag.png”); QIconSet iconset(pixmap); popup->insertItem(iconset,”Close”,this, SLOT(slotClose())); popup->insertSeparator(); popup->insertItem(“Exit”,this, SLOT(slotExit()),ALT+Key_X); menubar->insertItem(“&File”,popup); checkPopup = new QPopupMenu(); checkPopup->setCheckable(TRUE); enableColorsID = checkPopup->insertItem( “Enable Colors”,this,SLOT(slotEnableColors())); checkPopup->setItemChecked(enableColorsID,TRUE); enableGraphicsID = checkPopup->insertItem( “Enable Graphics”,this, SLOT(slotEnableGraphics())); checkPopup->setItemChecked(enableGraphicsID,FALSE); menubar->insertItem(“&Toggles”,checkPopup); popup = new QPopupMenu(); pixmap.load(“tinylogo.png”); popup->insertItem(pixmap,this,SLOT(slotLogo())); pixmap.load(“qtlogo.png”); popup->insertItem(pixmap,this,SLOT(slotLogo())); menubar->insertItem(“&Pixmaps”,popup); popup = new QPopupMenu(); popup2 = new QPopupMenu(); popup2->insertItem(“Horizontal”,this,SLOT(slotSub())); popup2->insertItem(“Vertical”,this,SLOT(slotSub())); popup->insertItem(“Orientation ”,popup2); menubar->insertItem(“Submenu”,popup); KHelpMenu *help = new KHelpMenu(this, “Text that will appear in\n” “a very simple About box”); popup = help->menu(); 4682-1 ch06.f.qc 11/13/00 14:10 Page 131 Chapter ✦ Menus and Toolbars 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 menubar->insertItem(“&Help”,popup); } void MenuMain::slotExit() { kapp->exit(0); } bool MenuMain::queryClose() { return(TRUE); } void MenuMain::slotEnableColors() { if(checkPopup->isItemChecked(enableColorsID)) checkPopup->setItemChecked(enableColorsID,FALSE); else checkPopup->setItemChecked(enableColorsID,TRUE); } void MenuMain::slotEnableGraphics() { if(checkPopup->isItemChecked(enableGraphicsID)) checkPopup->setItemChecked(enableGraphicsID,FALSE); else checkPopup->setItemChecked(enableGraphicsID,TRUE); } void MenuMain::slotNew() {} void MenuMain::slotSave() {} void MenuMain::slotSaveAs() {} void MenuMain::slotClose() {} void MenuMain::slotLogo() {} void MenuMain::slotSub() {} The mainline of the program, beginning on line 10, creates a MenuMain object, displays it, and calls exec() to wait for input The constructor of MenuMain, beginning on line 15, calls createMainWidget() to provide a widget to act as the main window, and then calls createMenu() to add the menu bar to the top of the window The method createMainWidget(), beginning on line 23, creates a pushbutton and installs it as the main window of the application The button is installed by the call to setView() on line 33 The call to QWhatsThis::add() on line 27 is called to relate some descriptive text with the button — the user can display the text from the Help menu The method createMenu() beginning on line 35 creates the menu bar and all of its members There is one menu bar inside the KTMainWindow widget, and its address is retrieved and stored in the menubar pointer on line 37 Actually, the menu bar does not exist until the menuBar() method is called, but subsequent menuBar() calls return the same menu bar pointer 131 4682-1 ch06.f.qc 132 11/13/00 14:10 Page 132 Part I ✦ Getting Started Each button appearing on the menu bar represents one QPopupMenu object The first one is created on line 42 and added to the menu bar on line 56 Between lines 42 and 56 a number of items are inserted in the pop-up menu, resulting in a menu that looks like the one shown in Figure 6-5 Figure 6-5: A menu with icons and accelerators The call to insertItem() on line 56 specifies that the name of the menu be “File,” and the accelerator key be Alt-F That is, writing the label as “&File” instead of simply “File” results in the letter being underlined when it is displayed; and pressing the Alt-F key combination will cause the menu to appear, just as if you had selected it with the mouse The up and down arrow keys can be used to locate a member of the menu; and the Return or Enter key will select it, just as if you had clicked it with the mouse The item labeled “New” is created with the call to insertItem() on line 43 The accelerator key is specified by the constant value ALT+Key_N This is a shortcut for selecting the menu item; whenever the application has the keyboard focus, typing ALT-N produces the same result as selecting the New entry with the mouse The accelerator key appears on the right, as you can see in Figure 6-5 Notice that the ampersand preceding the letter N causes it to be underlined; however, unlike the menu bar, this does not automatically assign an accelerator key You can underline, or not underline, as you choose The “Save As” selection has an accelerator key, but does not have a letter underlined The accelerator keys are specified by special values that specify the key and its modifiers Three modifiers are available: ALT, CTRL, and SHIFT You can use none, one, two, or all three of them in combination with a key For example, the “Save As” entry defined on line 47 uses both the CTRL and SHIFT modifiers Many keys can be used for accelerators The following list contains some of the more commonly used keys There are more keys defined than will appear on any one keyboard, but most of the ones in this list are common enough that they should be useful, although I have never seen a keyboard with 35 function keys If you have some special keys that you would like to use, look in the source of the Qt header file named qnamespace.h, where you will find more than 230 keys listed 4682-1 ch06.f.qc 11/13/00 14:10 Page 133 Chapter ✦ Menus and Toolbars Key_0 through Key_9 Key_Down Key_Period Key_Apostrophe Key_End Key_Plus Key_Asterisk Key_Enter Key_Print Key_A through Key_Z Key_Equal Key_QuoteDbl Key_Backslash Key_Escape Key_Return Key_BackSpace Key_F1 through Key_F35 Key_Right Key_Backspace Key_Home Key_ScrollLock Key_BraceLeft Key_Insert Key_Semicolon Key_BraceRight Key_Left Key_Slash Key_BracketLeft Key_Minus Key_Space Key_BracketRight Key_Next Key_SysReq Key_CapsLock Key_NumLock Key_Tab Key_Colon Key_PageDown Key_Underscore Key_Comma Key_PageUp Key_Up Key_Delete The Close menu item defined on lines 49 through 52 is shown in Figure 6-5 with an icon displayed on its left To this, the first step is to create a pixmap containing the graphics This is done on line 49 by loading the data from the local disk file named flag.png The second step is to create a QIconSet object from the pixmap, as is done on line 50 The menu item itself is created by the call to insertItem() on line 48, with the QIconSet inserted as the first argument; otherwise, the arguments are the same as before CrossReference Chapter 13, “Graphic Manipulation,” describes other ways to create pixmaps To complete the File menu, line 53 inserts the horizontal separator line that appears between Close and Exit Lines 54 and 55 create the Exit menu member Figure 6-6 shows a menu with a pair of checkable buttons that can be toggled on and off The checkmark appears only when the button has been toggled on In the figure, the Enable Colors button is on and the Enable Graphics button is off Figure 6-6: A menu with toggle buttons 133 4682-1 ch06.f.qc 134 11/13/00 14:10 Page 134 Part I ✦ Getting Started The Toggles menu is created on line 58 and inserted into the menu bar on line 74 The call to setCheckable() on line 59 configures the pop-up menu so that all of its items can be toggled on and off This way, you can turn any item on the pop-up menu into a toggled item simply by toggling it on and off The actual toggling is not automatic The two slots for the toggle buttons — on lines 97 through 110 — check the current state of the toggle by calling isItemCheck(), and then call setItemChecked() to toggle it to the other state Because of the arguments required to toggle buttons in the slot methods, it was necessary to store a pointer to the pop-up menu, along with the ID numbers of the two buttons, on lines 16 through 18 of the header file The ID numbers are the return values from itemInsert(), on lines 60 and 63, and are the only way you can address a specific item inside a pop-up menu Instead of text, you can decorate your menus with pixmaps Figure 6-7 shows a menu using pixmaps for buttons They work just like the text menu buttons, so they can have accelerator keys and be toggle buttons In the figure, you can see that one pixmap is larger than the other — it is up to you to size your pixmaps, because each menu item will expand to accommodate whatever you give to it Figure 6-7: A menu using pixmaps for buttons The pop-up menu with the pixmaps is created on lines 70 through 74 Notice that the same QPixmap object is used for both of the buttons — this works because the insertItem() method makes its own local copy The only difference between a pixmap and a text button is the type of the first argument — on lines 71 and 73, a QPixmap object reference is the first argument A submenu can be created by inserting one pop-up menu into another as one of its items Lines 76 through 81 create a second pop-up menu, named popup2, and insert it into its parent menu with the label “Orientation ” The resulting menu, when selected, looks like the one shown in Figure 6-8 Figure 6-8: A menu with a submenu 4682-1 ch06.f.qc 11/13/00 14:10 Page 135 Chapter ✦ Menus and Toolbars The KHelpMenu object is created on line 80 and installed as the rightmost member of the menu bar on lines 86 and 87 The resulting menu is shown in Figure 6-9 Figure 6-9: The layout of the standard help menu The “Contents” item, with the accelerator key F1, will display help text The text itself is provided by you as an HTML file The name of the file depends on the name of the application For this example, named menumain, the index file of the help tree for the English version is as follows: /usr/doc/kde/HTML/en/menumain/index.html The “What’s This” menu item will switch your application into a mode in which every widget on display can be selected to display explanatory text about itself In this example, the call to the static method QWhatsThis on line 24 inserts the explanatory text into the button used as the main window Making the selection from the menu changes the cursor to a question mark that, when used to select an item, will display the text The text is displayed in a window with a simple border and a yellow background, as shown in Figure 6-10 Figure 6-10: Text displayed as a response to “What’s this?” The two bottom buttons on the menu are the About boxes The default About box for the application is a simple block of text with an OK button, and there is a standard About box with information about the current version of KDE You can use KHelpMenu and replace the built-in About box with one of your own To this, extend the KHelpMenu class and include a slot named aboutApplication() Instead of popping up the default About box, this slot will be executed — and you can create your own About box and display it 135 4682-1 ch06.f.qc 136 11/13/00 14:10 Page 136 Part I ✦ Getting Started CrossReference You can find some examples of creating About boxes in Chapter Pop-up Menus A QPopupMenu object does not need to be connected to a QMenuBar A menu can be popped up in the middle of a widget All your application has to is specify the location and call the show() method The following example responds to the right mouse button by displaying a pop-up menu, as shown in Figure 6-11 Figure 6-11: A menu pops up from the middle of a widget MenuPopup Header 10 11 12 13 14 15 16 17 18 19 20 /* menupopup.h */ #ifndef MENUPOPUP_H #define MENUPOPUP_H #include class MenuPopup: public QWidget { Q_OBJECT public: MenuPopup(QWidget *parent=0,const char *name=0); protected: virtual void mousePressEvent(QMouseEvent *event); private: QPopupMenu *popup; private slots: void slotStub(); }; #endif On line 7, the class MenuPopup uses QWidget as its base class And, because it is a widget, it inherits the virtual protected method mousePressEvent(), which is called whenever the mouse pointer is within the widget and a mouse button is pressed 4682-1 ch08.f.qc 188 11/13/00 14:11 Page 188 Part II ✦ Step by Step There are a couple of special cursors in the list The cursor named BlankCursor has no graphic — the cursor simply disappears It is a valid cursor in that you can still move it around and try to find things to click on, but you can’t see it The other special cursor is the one named BitmapCursor For this to work, you must supply a cursor of your own making, which is the subject of the next section Designing Your Own Cursor A cursor is a rectangle of pixels Each pixel can be black, white, or transparent For example, the KDE default arrow cursor is a black arrow with a white outline All the other pixels are transparent Filling with one color and outlining with another makes the cursor visible no matter what background color the cursor passes over To create a cursor, you need to create a pair of bitmaps Both bitmaps must be the same height and width because one of them is a mask that overlays the other The masking is necessary because there is only one bit per pixel, but there are three ways to display a pixel: black, white, or transparent Figure 8-4 shows the shape of a 16 × 16 cursor The pixel at the top — the one with the diamond in it — is the hot spot for this cursor The hot spot is usually at the end of a pointer or at the center of cross hairs — it determines the exact cursor position that is reported to your application Figure 8-5 shows another bitmap that acts as the mask for the cursor The two bitmaps are combined using the rules in Table 8-1 Table 8-1 Cursor Bitmap Display Rules Cursor Bit Setting Cursor Mask Bit Setting Result 1 Black White 0 Transparent Figure 8-4: The definition of the shape of a cursor 4682-1 ch08.f.qc 11/13/00 14:11 Page 189 Chapter ✦ The Mouse and the Keyboard Figure 8-5: The definition of a cursor mask There are several utility programs that you can use to create the bitmaps describing the cursor One is supplied as part of the X11 system Normally found as /usr/ X11R6/bin/bitmap, it is quite easy to use to create 16 × 16 cursor images — just start the program running and select the pixels with the mouse You can learn more about this utility, and about bitmaps in general, in Chapter The following example uses the cursor bitmaps shown in Figures 8-4 and 8-5 to create a cursor MyCursor Header 10 11 12 13 /* mycursor.h */ #ifndef GRABMOUSE_H #define GRABMOUSE_H #include class MyCursor: public QWidget { public: MyCursor(QWidget *parent=0,const char *name=0); }; #endif MyCursor /* mycursor.cpp */ #include #include #include #include “mycursor.h” #define upleft_width 16 #define upleft_height 16 #define upleft_x_hot 189 4682-1 ch08.f.qc 190 11/13/00 14:11 Page 190 Part II ✦ Step by Step 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 #define upleft_y_hot static unsigned char upleft_bits[] = { 0x00, 0x00, 0x40, 0x00, 0xe0, 0x00, 0xf0, 0x01, 0xf8, 0x03, 0xfc, 0x07, 0xfe, 0x0f, 0xf0, 0x01, 0xf0, 0x01, 0xf0, 0x01, 0xf0, 0x01, 0xf0, 0x7f, 0xf0, 0x7f, 0xf0, 0x7f, 0xf0, 0x7f, 0x00, 0x00}; #define upleftmask_width 16 #define upleftmask_height 16 static unsigned char upleftmask_bits[] = { 0x40, 0x00, 0xe0, 0x00, 0xf0, 0x01, 0xf8, 0x03, 0xfc, 0x07, 0xfe, 0x0f, 0xff, 0x1f, 0xff, 0x1f, 0xf8, 0x03, 0xf8, 0x03, 0xf8, 0xff, 0xf8, 0xff, 0xf8, 0xff, 0xf8, 0xff, 0xf8, 0xff, 0xf8, 0xff}; int main(int argc,char **argv) { KApplication app(argc,argv,”mycursor”); MyCursor *mycursor = new MyCursor(); mycursor->show(); app.setMainWidget(mycursor); return(app.exec()); } MyCursor::MyCursor(QWidget *parent,const char *name) : QWidget(parent,name) { QBitmap upleft(upleft_width,upleft_height, upleft_bits,TRUE); QBitmap upleftmask(upleftmask_width,upleftmask_height, upleftmask_bits,TRUE); QCursor upleftCursor(upleft,upleftmask, upleft_x_hot,upleft_y_hot); setCursor(upleftCursor); resize(100,100); } The cursor body is defined on lines through 15 This format of the data is the actual output from the bitmap utility — it was simply inserted into the source code of the program The height and width of the cursor, and the location of the hot spot, all appear as defined constants You can make a cursor of just about any size you would like, but most cursors are either 16 × 16 or 32 × 32 pixels The bitmap used for the cursor mask is defined on lines 17 through 23 The procedure for turning bitmap data into a cursor occurs in the constructor, which begins on line 34 On line 37, the cursor bitmap data is used to create a QBitmap object In the same way, the mask is used to create a QBitmap on line 39 Notice that the defined constants are required so that the QBitmap constructor can determine the height and width that is to be applied to the array of bits Finally, using the two bitmaps and the location of the hot spot, the cursor is created on 4682-1 ch08.f.qc 11/13/00 14:11 Page 191 Chapter ✦ The Mouse and the Keyboard line 41 The call to setCursor() on line 43 installs the cursor image to the current window The result is shown in Figure 8-6 Figure 8-6: A custom cursor Keyboard Events Two events are issued from the keyboard One is issued when a key is pressed; the other is issued when the key is released This makes it possible for the software to determine which key combinations are being pressed For example, if the Shift key has been pressed and not released, a letter key should result in uppercase instead of lowercase Fortunately, the Qt library keeps track of the keys for you The following program displays the two-pane window shown in Figure 8-7 The panel on the right is set to receive keystroke information, and each keystroke is listed in the panel on the left Each line begins with a P or R, indicating whether this was a Press or Release event The number following the colon is the unique ID number of the key This is followed by a description of the key (for this example, however, they not all have descriptions) If the keyboard event was generated because a key was being held down, the word “repeat” appears on the right Figure 8-7: Displaying information from each keystroke Note Qt recognizes about 240 unique keys When you Include the Control, Alt, and Shift modifier key combinations, the total comes to almost 2,000 because many specialized keyboards have special keys and special characters If you are going to be working with the special keys, look in the file qnamespace.h for the complete list 191 4682-1 ch08.f.qc 192 11/13/00 14:11 Page 192 Part II ✦ Step by Step FollowKeyboard Header 10 11 12 13 14 15 16 17 18 19 20 /* followkeyboard.h */ #ifndef FOLLOWKEYBOARD_H #define FOLLOWKEYBOARD_H #include #include #include class FollowKeyboard: public QSplitter { Q_OBJECT public: FollowKeyboard(QWidget *parent=0,const char *name=0); public slots: void newline(QString &); private: QMultiLineEdit *edit; }; #endif FollowKeyboard 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 /* followkeyboard.cpp */ #include #include #include “keyboardsensor.h” #include “followkeyboard.h” int main(int argc,char **argv) { KApplication app(argc,argv,”followkeyboard”); FollowKeyboard *followkeyboard = new FollowKeyboard(); followkeyboard->show(); app.setMainWidget(followkeyboard); return(app.exec()); } FollowKeyboard::FollowKeyboard(QWidget *parent, const char *name) : QSplitter(parent,name) { edit = new QMultiLineEdit(this); edit->setMinimumWidth(80); edit->setReadOnly(TRUE); edit->setMinimumWidth(200); KeyboardSensor *sensor = new KeyboardSensor(this); sensor->setMinimumWidth(80); 4682-1 ch08.f.qc 11/13/00 14:11 Page 193 Chapter ✦ The Mouse and the Keyboard 27 28 29 30 31 32 33 34 35 36 connect(sensor,SIGNAL(description(QString &)), this,SLOT(newline(QString &))); resize(10,10); } void FollowKeyboard::newline(QString &str) { edit->insertLine(str); edit->setCursorPosition(5000,0); } The FollowKeyboard constructor, beginning on line 16, is a horizontal QSplitter widget that contains two widgets On the left is a QMultiLineEdit object that is used to display the text, and on the right is a KeyboardSensor widget that is used to receive keystroke information The slot method newline() on line 32 appends a string to the bottom of the text in the QMultiLineEdit object The call to setCursor Position() on line 35 makes the bottom line of the text window visible KeyboardSensor Header 10 11 12 13 14 15 16 17 18 19 20 21 22 /* keyboardsensor.h */ #ifndef KEYBOARDSENSOR_H #define KEYBOARDSENSOR_H #include #include #include class KeyboardSensor: public QWidget { Q_OBJECT public: KeyboardSensor(QWidget *parent=0,const char *name=0); private: void emitDescription(const QString &,QKeyEvent *); virtual void keyPressEvent(QKeyEvent *event); virtual void keyReleaseEvent(QKeyEvent *event); signals: void description(QString &); }; #endif This header file defines the class KeyboardSensor to be a QWidget The declarations of keyPressEvent() and keyReleaseEvent() on lines 16 and 17 override those in the QWidget base class, and they will be called once for each keystroke The signal description() on line 19 emits descriptions of each keystroke 193 4682-1 ch08.f.qc 194 11/13/00 14:11 Page 194 Part II ✦ Step by Step KeyboardSensor 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 /* keyboardsensor.cpp */ #include #include #include “keyboardsensor.h” KeyboardSensor::KeyboardSensor(QWidget *parent, const char *name) : QWidget(parent,name) { setFocusPolicy(QWidget::StrongFocus); setMinimumSize(300,300); } void KeyboardSensor::keyPressEvent(QKeyEvent *event) { emitDescription(QString(“P: “),event); } void KeyboardSensor::keyReleaseEvent(QKeyEvent *event) { emitDescription(QString(“R: “),event); } void KeyboardSensor::emitDescription( const QString &typeStr,QKeyEvent *event) { int key = event->key(); int ascii = event->ascii(); ButtonState state = event->state(); QString keyStr = QString(“%1”).arg(key); QString charStr = QString(“”); if(key == Key_Control) { charStr += QString(“Control”); } else if(key == Key_Alt) { charStr += QString(“Alt”); } else if(key == Key_Shift) { charStr += QString(“Shift”); } else { if(state & ControlButton) charStr += “Ctl-”; if(state & AltButton) charStr += “Alt-”; if(state & ShiftButton) charStr += “Shft-”; if(isgraph(ascii)) charStr += ascii + QString(“ “); else if(state & ControlButton) charStr += (ascii + 64) + QString(“ “); } if(event->isAutoRepeat()) 4682-1 ch08.f.qc 11/13/00 14:11 Page 195 Chapter ✦ The Mouse and the Keyboard 50 51 52 53 54 55 56 } charStr += “ repeat”; QString str = QString(“%1 %2 %3”) arg(typeStr).arg(keyStr).arg(charStr); emit description(str); Only one window on the display has the keyboard focus at any one time — any keystroke entered will go only to that one window Some windows are capable of receiving the focus and others are not The constructor, on line 6, calls set FocusPolicy() to specify the way in which this widget is to receive the keyboard focus By default, your widget will not receive the keyboard focus Table 8-2 contains a description of the possible focus settings Table 8-2 Settings to Control Focus Policy Name Description ClickFocus The focus moves to this widget only if selected by the mouse NoFocus This widget does not accept focus StrongFocus This policy is a combination of TabFocus and ClickFocus TabFocus Only the Tab key can be used to move the focus from one widget to another This is normally used with a collection of widgets in a dialog WheelFocus The focus can be changed to this widget using TabFocus, ClickFocus, or the movement of the mouse wheel The method keyPressEvent() and keyReleaseEvent() on lines 12 through 19 override virtual methods in the base class, and are called with each keystroke Both methods are passed a QKeyEvent object, and they pass it on to the method emit Description() to format it as a string The method emitDescription() beginning on line 20 extracts the data from the QKeyEvent and emits a description() signal with a descriptive string Each key has a unique number This number is retrieved from the QKeyEvent by the call to key() on line 27 If the key is a displayable ASCII character, the key value is the same as its ASCII value Nondisplayable keys are assigned larger numbers For example, as shown previously in Figure 8-7, the Shift key’s value is 4128; the Alt key is 4131; and the Return key is 4100 195 4682-1 ch08.f.qc 196 11/13/00 14:11 Page 196 Part II ✦ Step by Step The conditional code (on lines 30 through 35) determines whether the key is one of the three modifier keys If it is not, the code on lines 27 through 46 lists any modifiers that are being held down, and then displays the character itself (if it is displayable) The test on line 43 will be true if the character is displayable However, if the Control key is being held down, the character value itself is modified (adding 64 to any Control character reveals the original displayable character) Line 49 checks the Boolean method isAutoRepeat() to determine whether the key is being held down, causing the events to be automatically generated Summary The Qt library simplifies the processing of data coming from the mouse and the keyboard Events are formatted into a descriptive object and are directed to the correct widget This chapter explained the following: ✦ There can be a direct relationship between an event in the hardware and a method call in your application ✦ Any widget can monitor the mouse for both movement and mouse button clicks ✦ Changing the appearance of the mouse cursor will change it only for that one window and all of its child windows, unless a child window makes its own change ✦ Keyboard events are issued for every key press and every key release This chapter touched briefly on the graphic process required to create a custom cursor The following chapter explores graphic processing further, and uses graphic files to decorate window backgrounds, buttons, menus, and other parts of an application ✦ ✦ ✦ 4682-1 ch09.f.qc 11/13/00 14:11 Page 197 C H A P T E R Graphics File Formats ✦ ✦ ✦ ✦ In This Chapter T his chapter primarily concerns itself with loading graphic data from disk files and displaying it KDE is capable of recognizing and reading a number of formats of graphic files Everything that appears on the display has a window because it inherits the one from QWidget Also, every class that has a window is capable of displaying a pixmap (a full-color graphic) in its window Your program can get its graphic data from one of two locations It can be stored in a file on disk, in one of several formats, and your program can then read the file and convert the data into an internal pixmap Also, if you prefer, there is a way to convert the contents of the graphic file into C source code so it can be compiled directly into your program The two methods result in the same thing — a QPixmap object that can be used to paint a window Two Kinds of Graphics The two basic kinds of graphics are bitmaps and pixmaps: ✦ A pixmap is a rectangular array of pixel values Each value in the array represents a color for one pixel A pixmap can contain as many colors as you can load into your palette at any one time ✦ A bitmap is a rectangular array of bits in which each bit corresponds to one pixel A bitmap has only two colors — that is, each pixel is either “on” or “off.” Normally, this is displayed as black and white, but KDE enables you to display a bitmap using any two colors A bitmap is really just a special case of a pixmap, but it is used often enough that it has its own special file format Manipulating the two basic forms of graphic data Loading and displaying graphic data stored in files Decorating buttons and labels with icons Creating special modifications of a graphic to represent different states ✦ ✦ ✦ ✦ 4682-1 ch09.f.qc 198 11/13/00 14:11 Page 198 Part II ✦ Step by Step There seems to be no end to graphics file formats Thanks to a “universal” conversion utility, almost any graphics file format can be used inside a KDE application The convert utility (described in more detail later in this chapter) can convert a graphics file from some external format into a format that can be displayed For example, the following command shows how to convert a JPEG file into a pixmap — a form that can be compiled directly into your program: convert rickrack.jpeg rickrack.xpm If you want to include a bitmap (no color) in your program, you can make the conversion as follows: convert rickrack.jpeg rickrack.xbm The convert utility looks at the contents of the input file to determine what kind of file it is (it doesn’t trust the file suffix on input), and looks at the suffix of the output filename to determine what kind of graphics file to produce The XPM Format The XPM (XPixMap) graphics format is a standard in X11 for storing graphics as ASCII text This format enables you to use your text editor to create or modify simple color graphics Not only is an XPM definition ASCII, but its format is C source code that you can compile directly into your program The following is an example of an XPM graphic with four colors: 10 11 12 13 14 15 16 17 18 19 20 21 22 23 /* XPM */ /** essPixmap.xpm **/ static const char *essPixmap[] = { “12 14 1”, “ c None”, “X c #FFFFFF”, “R c Red”, “B c #0000FF”, “ RRBB “, “XXXXXXXXXXXX”, “XXXXXXXXXXXX”, “XX RRBB “, “XX RRBB “, “XX RRBB “, “XXXXXXXXXXXX”, “XXXXXXXXXXXX”, “ RRBB XX”, “ RRBB XX”, “ RRBB XX”, “XXXXXXXXXXXX”, “XXXXXXXXXXXX”, “ RRBB “, }; 4682-1 ch09.f.qc 11/13/00 14:11 Page 199 Chapter ✦ Graphics File Formats The syntax of this XPM file is defined as an array of character strings The comment on the first line must be present because it is used by utilities to determine the file type Line contains four numbers that are used to describe the data that follow The first number specifies that the pixmap is 12 pixels wide, and the second number specifies that it is 14 pixels high The next number specifies that four colors are used in drawing the graphic The last digit specifies that one letter is used as the tag for each of the colors Lines through are the color definitions Each string begins with a character that is to be used as the tag that will identify the color Any ASCII character can be used Line defines the space character as the color named None This specifies that no pixel is to be painted, which produces transparency because the background is not overwritten Line assigns the value of white to the letter X The hexadecimal value FFFFFF is the red-green-blue value for white (in base 10, the values are 255 255 255) Line uses the hexadecimal value 0000FF to assign the color blue to the letter B Line uses a name to define a color for the letter R — the name must be one of the RGB names found in the file /usr/X11R6/lib/X11/rgb.txt The graphic itself begins on line and concludes with line 22 Each string is 12 characters long because the graphic is 12 pixels wide and only character is used to represent a pixel There are 14 of these strings because the graphic is 14 pixels high Every pixel is assigned a value by containing one of the color characters defined earlier An XPM file can be used to contain large, high-resolution images with a large number of colors For example, the Linux distribution includes a file named logo.gif that contains the Linux penguin You can convert the GIF file to an XPM file with the following command: convert logo.gif logo.xpm In the resulting XPM file, more than 24 bits of color information are included, which means there are more colors than can be represented by single characters The entire XPM file is 560 lines long Here is an excerpt: /* XPM */ static const char *magick[] = { “257 303 251 2”, “ c Gray0”, “ c #080800000404”, “X c #080808080000”, “o c Gray3”, “O c #101004040404”, “+ c #101010100404”, “{ c #f0f0b8b80808”, “} c #f8f8b0b00808”, “| c #f8f8b8b80808”, 199 4682-1 ch09.f.qc 200 11/13/00 14:11 Page 200 Part II ✦ Step by Step “ X “.X “XX “BX “VX “CX “ZX “AX “SX “DX “FX “GX “HX “JX c #f0f0b0b01010”, c #f0f0b8b81010”, c #f8f8b8b81010”, c #d8d8d8d8e8e8”, c #e0e0e0e0d8d8”, c #f0f0e8e8d8d8”, c Gray88”, c Gray91”, c #e8e8e8e8f0f0”, c #f0f0e8e8ecec”, c #f0f0f0f0e8e8”, c Gray94”, c #f8f8f8f8f8f8”, c None”, This XPM graphic is 257 pixels wide and 303 pixels tall It contains a total of 251 colors and uses characters to represent each color The first few characters may appear to be defined by a single character, but, in fact, characters are used because the blank serves as the second character As you can see later in the file, the period and X characters are used Because characters are required to specify a color, each string defining a row of pixel values has to be 514 characters long (twice 257) Also, notice that the hexadecimal numbers for the colors have 12 digits instead of This is still an RGB format, but each color is 16 bits (4 hexadecimal digits) Either length is valid for an XPM file — the software that reads it counts the digits to determine the format The colors in the file /usr/X11R6/lib/X11/rgb.txt, and many colors found in other places, are defined as three 8-bit values The following simple program converts three 8-bit values into both the long and short hexadecimal strings required by XPM: /* hexcolor */ #include #include char *usage[] = { “ Usage: hexcolor r g b”, “ Enter the three RBG color values in the”, “ range of to 256 The output is both a”, “ 24-bit and 48-bit hexadecimal number of the”, “ color that can be used in an XPM file.” }; int main(int argc,char *argv[]) { int i; int r,g,b; if(argc < 4) { for(i=0; isetFixedSize(pixmap.width(),pixmap.height()); widget->setBackgroundPixmap(pixmap); widget->show(); app.setMainWidget(widget); return(app.exec()); } The #include statement on line causes the XPM data to be compiled directly into the program Line 11 creates a QPixmap from the XPM data 201 4682-1 ch09.f.qc 202 11/13/00 14:11 Page 202 Part II ✦ Step by Step Any widget can be used to display a pixmap as its background; therefore, for this example, a generic widget is created on line 12 The call to setFixedSize() on line 13 causes the widget to be exactly the same size as the pixmap The call to setBackgroundPixmap() on line 14 inserts the pixmap into the widget The result is shown in Figure 9-1 Figure 9-1: Displaying compiled XPM data If you set your window to a fixed size, and you have a pixmap of that exact size, the pixmap is shown in its entirety If the widget’s window is smaller than the pixmap, the image is trimmed on the bottom and on the right If the window is larger than the pixmap, the pixmap is tiled until it fills the window The following example uses the smaller pixmap (defined earlier in this chapter as essPixmap) to tile the background of a widget: 10 11 12 13 14 15 16 17 18 /* showxpmtile.cpp */ #include #include #include #include “essPixmap.xpm” int main(int argc,char **argv) { KApplication app(argc,argv,”showxpmtile”); QPixmap pixmap(essPixmap); QWidget *widget = new QWidget(); widget->setBackgroundPixmap(pixmap); widget->resize(200,100); widget->show(); app.setMainWidget(widget); return(app.exec()); } ... slotEnableGraphics(); 30 private: 31 void createMainWidget(); 32 void createMenu(); 33 }; 34 35 #endif MenuMain 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 /* menumain.cpp... 4682-1 ch06.f.qc 11/ 13/ 00 14:10 Page 139 Chapter ✦ Menus and Toolbars ToolbarMain 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48... 4682-1 ch06.f.qc 11/ 13/ 00 14:10 Page 1 43 Chapter ✦ Menus and Toolbars 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58